[GauntletWizard]

I think it's to serve the very large and very real market of people without credit cards. I guarantee they're not paying 2.9% credit card transactions; At their bulk they've got incredible deals with every card provider. I'm also sure they're giving a percent or more to the store accepting cash for them - Similar to gift card buying models.

7% of the US, a first world nation with amazing credit services, is unbanked[1]. From that same source, nearly 20% is underbanked - As in, they still go to Check-cashing places and get cash directly, rather than getting direct-deposit.

[1]http://fortune.com/2016/09/08/unbanked-americans-fdic/